MUTATIONS Flashcards
What is a mutation
A change in structure of a gene due to a change in a section of a gene or alteration to the chromosome where the gene is located
What are gene mutations
Mutations that affect small regions of DNA, usually one base (point mutation)
Occur during the s phase of the cell cycle
What are chromosome mutations
Mutations that affect large regions of DNA that is contained within chromosomes
Occurs during metaphase of meiosis
What are mutagenic agents
Increase the rate of reactions
What are the two types of mutagenic agents
Carcinogens - cause a mutation in one cell that leads to tumor growth
Mutagen - causes mutation in one cell or an entire organism that can be inherited
Effect of radiation regarding mutation
High energy ionising radiation such as x-rays uv or alpha radiation ionise bases or affect bonding of correct base pairs
Effect of chemicals regarding mutation
Intercalating (separates DNA strand)
E.g. mustard gas, agent orange or asbestos
How can viruses cause mutation
Some viruses such as HPV can change the base sequence in DNA causing genetic disease and cancer
Three types of point mutations
Substitution missense
Substitution nonsense
Deletion
What is substitution reaction
A change in a single nucleotide base (pair)
What is a substitution missense mutation
Results in a single amino acid change
What is a substitution nonsense mutation
A substitution that results in a stop codon instead of an amino acid, usually resulting in a non-functional protein
Deletion mutations
Either a single base (point) or a section of the gene is missed during replication
Results in a frame shift where subsequent codons within the gene are also effected
Overall effect of a base substitution or deletion
- Change in base sequence could lead to a change in the amino acid sequence
- This would lead to a change in the tertiary structure of the protein as
- Bonds (ionic/hydrogen) would be in different places
What feature of the genetic code makes substitution mutations less harmful
Degenerate- substitution mutations can still code for the correct amino acid
Code is a triplet and non- overlapping so introducing or deleting a base causes a frame shift or nonsense where subsequent codons are also effected whereas substitution can only affect one codon (missense)
